Arctic ecology is the scientific study of the relationships between biotic and abiotic factors in the arctic, the region north of the Arctic Circle (66 33â€™). This is a region characterized by stressful conditions as a result of extreme cold, low precipitation, a limited growing season (50â€“90 days) and virtually no sunlight throughout the winter. The Arctic consists of taiga (or boreal forest) and tundrabiomes, which also dominate very high elevations, even in the tropics. Sensitive ecosystems exist throughout the Arctic region, which are being impacted dramatically by global warming.

Arctic environment

To understand Arctic ecology, it is important to consider both the terrestrial and oceanic aspects of the region. A few important parts of this environment are sea ice and permafrost.

Sea ice is frozen seawater that moves with oceanic currents; it provides important habitat and a resting place for animals, particularly during the winter months. Over time, small pockets of salty seawater get trapped in the ice, and the salt is squeezed out. This causes the ice to become progressively less salty. Sea ice persists throughout the year, but there is less ice available during summer months.

Large portions of the land are also frozen during the year. Permafrost is substrate that has been frozen for a minimum of 2 years. There are two types of permafrost: discontinuous and continuous. Discontinuous permafrost is found in areas where the mean annual air temperature is only slightly below freezing (0|Â°C|Â°F|0|abbr=on|lk=on|disp=s); this forms in sheltered locations. In areas where the mean annual soil surface temperature is below -5|Â°C|Â°F|0|abbr=on|lk=off, continuous permafrost forms. This is not limited to sheltered areas and ranges from a few inches below the surface to over 300|m|ft|-2|abbr=on|lk=off deep. The top layer is called the active layer. It thaws in the summer and is critical to plant life.

Biomes

Moisture and temperature are major physical drivers of natural ecosystems. The more arid and colder conditions found at higher northern latitudes (and high elevations elsewhere) support tundra and boreal forests. The water in this region is generally frozen and evaporation rates are very low. Species diversity, nutrient availability, precipitation, and average temperatures increase as you move from the tundra to boreal forests and then to deciduoustemperate ecosystems, which are found south of these Arctic biomes.

Tundra

Tundra is found from 55 Â° to 80Â° N latitude in North America, Eurasia and Greenland. It can be found at lower latitudes at high elevations as well. The average temperature is -34|Â°C|Â°F|0|abbr=on|lk=off; during the summer it is less than 10|Â°C|Â°F|abbr=on|lk=off. Average precipitation ranges from 10|to|50|cm|in|0|abbr=on|lk=off, and the permafrost is 400|-|600|m|ft|-2|abbr=on|lk=off thick. Plant species supported by tundra have small leaves, are short (74&nbsp;mm to <5 m), tend to be deciduous, have a high ratio of roots to shoots, and are composed mainly of perennial forbs, dwarf shrubs, grasses, lichens, and mosses.

Boreal

In comparison to tundra, boreal forest has a longer and warmer growing season and supports larger species diversity, an increase in canopy height, vegetation density, and biomass. Boreal conditions can be found across northern North America and Eurasia. The boreal forests in the interior of the continents grow on top of permafrost due to very cold winters (see drunken trees), while much of the boreal forest has patchy permafrost or lack permafrost completely. The short (3â€“4 month) growing season in boreal forests is sustained by greater levels of rainfall (between 30|and|85|cm|in|abbr=on|lk=off|disp=s per year) than the tundra receives; This biome is dominated by closed canopy forests of evergreen conifers, especially spruces, fir, pine and tamarack with some diffuse-porous hardwoods. Shrubs, herbs, ferns, mosses, and lichens are also important species. Stand-replacing crown fires are very important to this biome, occurring as frequently as every 50â€“100 years in some parts.

Adaptations to conditions

Humans

Humans living in the Arctic region generally rely on warm clothing and buildings to protect them from the elements. Acclimatization, or the adjustment to new conditions, appears to be the most common form of adaptation to cold environments. No genetic advantage has been found when different people groups or races are compared. There is no evidence that fat is grown in response to cold, although its presence is advantageous. Amazingly, most people living in the Arctic region live a lifestyle very connected to the environment, spending significant time outside and depending heavily on hunting and fishing.

Other animals

Animals that are active in the winter have adaptations for surviving the intense cold. A common example is the presence of strikingly large feet in proportion to body weight. These act like snowshoes, and can be found on animals like the snowshoe hare and caribou. Many of the animals in the Arctic are larger than their temperate counterparts (Bergmannâ€™s rule), taking advantage of the smaller ratio of surface area to volume that comes with increasing size. This increases the ability to conserve heat. Layers of fat, plumage, and fur are also very effective insulators to help retain warmth and are common in Arctic animals including polar bears and marine mammals. Some animals also have digestive adaptations to improve their ability to digest woody plants either with or without the aid of microbial organisms. This is highly advantageous during the winter months when most soft vegetation is beneath the snow pack.

Not all Arctic animals directly face the rigors of winter. Many migrate to

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Question:I left my book in class!

Answers:An ecological pyramid shows relationships between trophic levels. There are 3 common types: Numbers, Biomass, and Energy.
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Question:Describe the 3 different types of ecological pyramids

Answers:Ecologists represent the relative amounts of energy in an ecosystem in an ecological pyramid. The pyramid is divided into sections, each representing one trophic level. An ecological pyramid can show energy, biomass or the number of organisms in a food web (a community of organisms where there are several interrelated food chains).
A pyramid of numbers shows the number of organisms at each trophic (relating to nutrition) level. In pyramids of numbers, each successive trophic level is occupied by fewer organisms. Thus the number of herbivores like zebras and wild beasts is greater than the carnivores like lions.
A pyramid of biomass illustrates the total biomass at each successive trophic level. Biomass is the total amount of living matter at a trophic level. The pyramids of mass show a progressive reduction of biomass in the successive trophic level. The pyramids of mass show a progressive reduction of biomass in the successive trophic levels.
A pyramid of energy indicates the energy content in the biomass of a trophic level. These pyramids shown that less energy reaches each successive trophic from the level beneath it because some of the energy at the lower level is used by the organisms to perform work, while some of it is lost.
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Question:

Answers:An energy pyramid tells the amount of energy at each trophic level; a number pyramid tells the number of organisms at each trophic level; a biomass pyramid tells the amount of dry biomass at each trophic level.

Question:I'm supposed to have 3 food chains-
-energy food chain, biomass food chain, and a numbers food chain.
Their each different and i don't understand but i know they have to do with "trophic levels"...someon please help!

Answers:Ecological pyramid (Eltonian pyramid) - Graphical representation of the trophic structure and function of an ecosystem. The first trophic level, of producer organisms (usually green plants), forms the base of the pyramid, with succeeding levels added above to the apex. There are three types of pyramids: of numbers, of biomass, and of energy.
An example of each is in the second link.

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Ecological pyramids :Check us out at www.tutorvista.com An ecological pyramid (or trophic pyramid) is a graphical representation designed to show the biomass or productivity at each trophic level in a given ecosystem. Biomass pyramids show the abundance or biomass of organisms at each trophic level, while productivity pyramids show the production or turnover in biomass. Ecological pyramids begin with producers on the bottom (such as plants) and proceed through the various trophic levels (such as herbivores that eat plants, then carnivores that eat herbivores, then carnivores that eat those carnivores, and so on). The highest level is the top of the food chain. In Ecological Pyramid the arrangements from below is producers then primary consumers then secondary consumers and on the top is decomposers